I think that paying for resquests would be problematic and unfair for modders, and finally detrimental to mod creation.
Anyway, most mods take hours to make, so asking 5 or 10 euros/dollars seems like an insult to me. If I really needed money, I'd go do extra hours in McDonald's, it would be more efficient...
Also, what about modders that make mods without requests and these mods get dowloaded much more that some obscure request?
Examples:
random furry $#!+ (requested, 2-3 hours of work + 30 minutes cos requester didn't like the ears), 837 dowloads since June 2016.
Rem (done on my own, 4-5 hours of work), 4,436 downloads since June 2016.
animtools (done by sby, 28th version, probably dozens of hours of work, or even more), 132,369 downloads since February 2016.
Also, what about helping new users or making tutorials so newbies can make mods themselves?
An option could be to be paid for each download from the ad revenues of the site (I have really no idea how much the total could be).
With this, I could buy a pair of socks, and sby
the latest Maserati.
Anyway, I don't need new socks, so I'll continue to provide my mods for free...
Bringing money would only bring problems in my opinion, but every modder is free to ask to be paid or even adding Patreon or PayPal links to his mods or signature (I am thinking about it for a long time indeed...).